You are driving a 14 year old vehicle. Syncros are wear items. After 14 years, they will be worn.

I really do not think the flywheel had anything to do with it. Actually, I don't see how it could ever come close to causing the problem.

I agree with the above. Right now, bleed/replace the hydraulics and change the fluid in the transmission. At the best, it will make it driveable. At the worst, it is time for a new/used tranny or a rebuild.

Good Luck,
Michael